Aerodynamic bearing assembly for spindle motor for hard disk drives

ABSTRACT

Disclosed is an aerodynamic bearing assembly for a spindle motor for hard disk drives, in which a hub of the spindle motor is pivoted in both radial and thrust directions by the ball bearing, which directly contacts the center of the hub, to perform rotation according to the rotational principle of a whirligig, and is subject to the thrust load through the aerodynamic bearing assembly with air groove(s) without being in contact with it, so that the hub maintains a rotational center without mechanical contact resulting in noise and starting failure of the assembly during an initial starting (low-speed rotation). The assembly includes air grooves, the air groove generating aerodynamic pressure between the hub and the aerodynamic bearing while the hub rotates.

FIELD OF INVENTION

The present invention relates to a spindle motor for hard disk drives.More particularly, the present invention relates to an aerodynamicbearing assembly for a spindle motor for hard disk drives capable ofpivoting a lower portion of a hub in both radial and thrust directionsthrough use of a ball bearing, which comes into direct contact with thelower portion of the hub, so that a rotational center of the hub can bemaintained without mechanical contact resulting in noise and startingproblems of the aerodynamic bearing assembly during an initial starting(during low-speed rotation).

BACKGROUND ART

Generally, a hard disk drive functions as an auxiliary memory unit of acomputer, and is comprised of a platter, a head, a spindle motor, a headarm and a printed circuit board. The hard disk drive helps to operatethe system of a computer either by reading out and regeneratinginformation stored at the platter through the head or by writing newinformation on the platter through the head.

In the construction of the above-mentioned hard disk drive, the platteris a metallic circular plate coated with magnetic material, functioningto write various data. The platter is stacked in layers and rotatesabout a rotatable shaft. This rotatable shaft is named a spindle shaft.A motor for rotating the spindle shaft is named a spindle motor.

The head for reading/writing data stored at the platter is connected tothe head arm so as to access desired information addresses. This headarm is driven by a head actuator, which is called a voice coil motor(VCM). A conventional spindle motor will be described below.

FIG. 1 is an exploded perspective view of a conventional spindle motorfor hard disk drives employing at least one ball bearing, and FIG. 2 isa cross sectional view of the spindle motor of FIG. 1.

As shown in FIGS. 1 and 2, the conventional spindle motor 10 for harddisk drives employing at least one ball bearing comprises a base 11serving for a lower portion of the spindle motor; a spindle shaft 12fitted at a center of the base in a vertical direction; a first ballbearing 13 fitted on a lower portion of the spindle shaft 12 positionedon the upper side of the base 11; a stator 14 fitted around the firstball bearing 13 and constructed in such a manner that a coil 14 b iswound around a core 14 a of the stator; a second ball bearing 15 fittedon an upper portion of the spindle shaft 12; a hub 16, being rotatableabout the first and second ball bearings 13 and 15, for covering theupper portion of the base 11; and an annular permanent magnet 17 fittedon an inner circumferential surface of a lower portion of the hub 16 andgenerating driving force for rotating the hub 16 through use of themagnetic field produced in cooperation with the coil 14 b.

In the conventional spindle motor 10 for hard disk drives constructed asmentioned above, when power is supplied to the coil 14 b of the stator14, a magnetic field (not shown) is established between the coil 14 band the permanent magnet 17. The magnetic field between the coil 14 band the permanent magnet 17 allows the hub 16 to be rotated in onedirection.

However, the construction wherein the hub 16 rotates using the first andsecond ball bearings 13 and 15 makes it impossible to drive at a highspeed with a strict rotational precision, which results in generatingnoise and vibration when the ball bearing rotates at a high speed. Thefollowing description will be made regarding the construction of anaerodynamic bearing shown in FIG. 3.

FIG. 3 is a cross-sectional view of a conventional spindle motor forhard disk drives employing at least one aerodynamic bearing.

The conventional spindle motor 20 for hard disk drives employing atleast one aerodynamic bearing shown in FIG. 3 includes a base 21 formedas a lower portion of the spindle motor, a first ball bearing 22 fittedon an upper central portion of the base 21, a stator 23 fitted aroundthe first ball bearing 22 and constructed in such a manner that a coil23 b is wound around a core 23 a of the stator, a spindle shaft 24fitted on an upper central portion in a vertical direction, a secondbearing 25 fitted on an upper portion of the spindle shaft 24, asupported hub 26 that is rotatable about the spindle shaft 24 andconstructed to cover the upper portion of the base 21, first and secondaerodynamic bearings 27 and 28 fitted on an inner upper portion of thehub 26 for generating aerodynamic pressure for smoothly rotating the hub26 about the spindle shaft 24, and a permanent magnet 27 fitted on aninner circumferential surface of a lower portion of the hub 16 forgenerating driving force for rotating the hub 26 through use of themagnetic field produced in cooperation with the coil 23 b.

In the conventional spindle motor 20 for hard disk drives employing atleast one aerodynamic bearing constructed as mentioned above, when poweris supplied to the coil 23 b of the stator 23, a magnetic field (notshown) is established between the coil 23 b and the permanent magnet 27.The magnetic field between the coil 23 b and the permanent magnet 27allows the hub 26 to be rotated in one direction.

Once the hub 26 rotates, air begins to flow on the inner surfaces of thefirst and second aerodynamic bearings 27 and 28. The faster the hub 26rotates, the stronger the air flows. As a result, the flow of air ischanged into a layer of air having a predetermined rigidity between thefirst and second aerodynamic bearings 27 and 28, the spindle shaft 24,the first bearing 25, and the second bearing 22 in proportion to therotational speed of the hub 26. Therefore, the hub 26 with a mountedplatter (not shown) rotates about the spindle shaft 24 while overcomingthe imposed load and disturbance from the air layer acting as a bearingbetween the spindle shaft 24 and the hub 26.

However, the conventional spindle motor for hard disk drives employingat least one aerodynamic bearing, constructed as mentioned above,enables rigidity of the air layer to be improved at a low-speedrotation, but rigidity of the air layer is maintained almost constantlywithout an increase in proportion to the rotational speed when the motorrotates beyond a fixed speed.

Further, the conventional spindle motor for hard disk drives employingat least one aerodynamic bearing constructed as mentioned above isdesigned so that the base is assembled with the first ball bearing, butthe spindle shaft is assembled with the second bearing, so that theassembled two sets maintain a predetermined size of air gap with respectto the aerodynamic bearings. Therefore, there are problems in that thespindle motor has a reduced assembly capability and has a difficulty inconstantly maintaining a constant thickness of the air gap. Moreover,the spindle motor is designed so that the hub is supported around thespindle shaft via the air gap without putting the hub into directcontact with the spindle shaft. Therefore, during initial starting, thespindle motor is subjected to malfunction, attrition losses of theaerodynamic bearings as well as the first and second ball bearings,noise and vibration, all of which are caused by friction.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of theabove-mentioned problems, and it is an object of the present inventionto provide an aerodynamic bearing assembly for a spindle motor for harddisk drives, in which a rotatable hub of the spindle motor for hard diskdrives is adapted not only to be pivoted in both radial and thrustdirections by the ball bearing coming into direct contact with thecenter of the hub so as to perform rotation according to the rotationalprinciple of the whirligig, but also to be subjected to the thrust loadthrough the aerodynamic bearing assembly with the air groove(s) withoutbeing in contact with it, so that the hub can maintain a rotationalcenter without mechanical contact resulting in noise and startingfailure of the aerodynamic bearing assembly during an initial starting(during low-speed rotation).

It is another object of the present invention to provide an aerodynamicbearing assembly for a spindle motor for hard disk drives, in which ahub, which is designed to have a conical structure like a whirligig anda rotatable point-contact supporting structure through the ball bearing,is combined with the aerodynamic bearing having at least one air groove,which is formed on at least one of the upper horizontal surface of themain bearing body of the aerodynamic bearing, the outer circumferentialsurface of the main bearing body of the aerodynamic bearing, the lowerhorizontal surface of the hub and the inner circumferential surface ofthe cylindrical section of the hub, so that rotational rigidity of thebearing against disturbance during high-speed rotation rather thanduring low-speed rotation as well as the capability of rotating withouta slant are improved, and thus an excellent rotational precision can beobtained.

It is yet another object of the present invention to provide anaerodynamic bearing assembly for a spindle motor for hard disk drives,in which a hub is designed to have a conical structure like a whirligigand a rotatable point-contact supporting structure through the ballbearing, so that even though static electricity is generated by frictionbetween the air caused by a high-speed rotation and the platter, thestatic electricity can be discharged through the ball bearing, thusimproving a structural safety of the spindle motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is an exploded perspective view of a conventional spindle motorfor hard disk drives employing at least one ball bearing;

FIG. 2 is a cross-sectional view of the spindle motor of FIG. 1;

FIG. 3 is a cross-sectional view of a conventional spindle motor forhard disk drives employing at least one aerodynamic bearing;

FIG. 4 is an exploded perspective view of a spindle motor for hard diskdrives with a pivot structure according to the present invention;

FIG. 5 is a partially sectional perspective top view of a spindle motorfor hard disk drives with a pivot structure according to the presentinvention;

FIG. 6 is a partial sectional perspective bottom view of a spindle motorfor hard disk drives with a pivot structure according to the presentinvention;

FIG. 7 is a cross-sectional view of an assembled spindle motor for harddisk drives with a pivot structure according to the present invention;

FIG. 8 is a perspective view of a first embodiment of an aerodynamicbearing assembly of a spindle motor for hard disk drives with a pivotstructure according to the present invention.

FIG. 9 is a cross-sectional view of a spindle motor for hard disk driveswith a pivot structure according to one embodiment of the presentinvention;

FIG. 10 is a cross-sectional view showing a spindle motor for hard diskdrives with a pivot structure according to another embodiment of thepresent invention;

FIG. 11 is a perspective view of a second embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention;

FIG. 12 is a perspective view of a third embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention;

FIG. 13 is a perspective view of a fourth embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention;

FIG. 14 is a perspective view of a fifth embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention;

FIG. 15 is a perspective view of a sixth embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention;

FIG. 16 is a perspective view of a seventh embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention;

FIG. 17 is a perspective view of an eighth embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention;

FIG. 18 is a cross-sectional view of a ninth embodiment for anaerodynamic bearing assembly of a spindle motor with a pivot structureaccording to the present invention;

FIG. 19 is a cross-sectional view of a tenth embodiment for anaerodynamic bearing assembly of a spindle motor with a pivot structureaccording to the present invention; and

FIG. 20 is a cross-sectional view of an eleventh embodiment for anaerodynamic bearing assembly of a spindle motor with a pivot structureaccording to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In order to accomplish the above-mentioned objects, there is provided anaerodynamic bearing assembly employed in a spindle motor for hard diskdrives, the spindle motor including a base, a hub, a stator and apermanent magnet, the base serving as a lower portion of the spindlemotor, the hub being rotatably fitted on the base and able to fixedlymount a platter, the stator being formed with a plurality of cores woundaround by one or more coils along an outer circumference of the statorand being formed with an open press-fit portion at the center of thestator. The permanent magnet is fitted on an inner circumferentialsurface of the hub and generates a magnetic field in cooperation withthe coil. The aerodynamic bearing assembly comprises an aerodynamicbearing including a main bearing body formed in a concentric disk shapeto serve as an upper portion of the aerodynamic bearing, and anauxiliary bearing body integrally formed on a lower portion of the mainbearing body and press-fitted into the open press-fit portion of thestator to fixedly mount the stator on an outer circumferential surfaceof the auxiliary bearing body, the aerodynamic bearing being fixedlyinstalled in a space between the base and the hub; and a ball bearingfor rotatably pivoting a center of the hub in both radial and thrustdirections at a center of the aerodynamic bearing, wherein at least oneof an upper horizontal surface of the main bearing body of theaerodynamic bearing, an outer circumferential surface of the mainbearing body of the aerodynamic bearing, a lower horizontal surface ofthe hub and a lower inner circumferential surface of the hub, isprovided with at least one air groove having a predetermined depth. Theair groove generates aerodynamic pressure between the hub and theaerodynamic bearing while the hub rotates.

In the above-mentioned construction, the air groove may be formed on theupper horizontal surface of the main bearing body of the aerodynamicbearing, or on the outer circumferential surface of the main bearingbody of the aerodynamic bearing, or both on the upper horizontal surfaceof the main bearing body of the aerodynamic bearing and on the outercircumferential surface of the main bearing body of the aerodynamicbearing.

Meanwhile, the air groove may be formed on the lower horizontal surfaceof the hub, or on the lower inner circumferential surface of the hub, orboth on the lower horizontal surface of the hub and on the lower innercircumferential surface of the hub.

Further, the air groove may be formed both on the upper horizontalsurface of the main bearing body of the aerodynamic bearing and on thelower inner circumferential surface of the hub, or both on the outercircumferential surface of the main bearing body of the aerodynamicbearing and on the lower horizontal surface of the hub.

In the above-mentioned constructions, the upper horizontal surface ofthe main bearing body of the aerodynamic bearing may be further providedwith at least one oilless bearing in a ring shape. Here, one or more airgroove is formed in a predetermined depth on an upper surface of theoilless bearing.

Further, the oilless bearing may be mounted on the lower horizontalsurface of the hub in a ring shape. Here, one or more air groove isformed in a predetermined depth on a lower surface of the oillessbearing.

On the other hand, at least one pair of oilless bearings opposite toeach other may be formed on the upper horizontal surface of the mainbearing body of the aerodynamic bearing and on the lower horizontalsurface of the hub in a ring shape. Here, of the opposite oillessbearings, one, which is mounted on the upper horizontal surface of themain bearing body of the aerodynamic bearing, may be provided with anair groove on an upper surface thereof, while the other, which ismounted on the lower horizontal surface of the hub, may be provided withan air groove on a lower surface thereof.

According to the present invention, as mentioned above, the ball bearingfor rotatably supporting the hub is arranged at a rotational center ofthe aerodynamic bearing to be at a lower position than an upperhorizontal plane of the main bearing body of the aerodynamic bearing, sothat the ball bearing has a rotatable supporting point at the lowerposition than the upper horizontal plane of the main bearing body of theaerodynamic bearing.

Alternatively, the ball bearing for rotatably supporting the hub may bearranged at a rotational center of the aerodynamic bearing to be flushwith an upper horizontal plane of the main bearing body of theaerodynamic bearing, so that the ball bearing has a rotatable supportingpoint flush with the upper horizontal plane of the main bearing body ofthe aerodynamic bearing.

Further, the ball bearing for rotatably supporting the hub may bearranged at a rotational center of the aerodynamic bearing to be at ahigher position than an upper horizontal plane of the main bearing bodyof the aerodynamic bearing, so that the ball bearing has a rotatablesupporting point at the higher position than the upper horizontal planeof the main bearing body of the aerodynamic bearing.

Hereinafter, the preferred embodiments of the present invention will bedescribed in detail with reference to the drawings.

FIG. 4 is an exploded perspective view of a spindle motor for hard diskdrives with a pivot structure according to the present invention, FIG. 5is a partially sectional perspective top view of a spindle motor forhard disk drives with a pivot structure according to the presentinvention, FIG. 6 is a partially sectional perspective bottom view of aspindle motor for hard disk drives with a pivot structure according tothe present invention, FIG. 7 is a cross-sectional view of an assembledspindle motor for hard disk drives with a pivot structure according tothe present invention, FIG. 8 is a perspective view of a firstembodiment of an aerodynamic bearing assembly of a spindle motor forhard disk drives with a pivot structure according to the presentinvention.

As shown in FIGS. 4 to 8, a spindle motor 100 for a hard disk driveaccording to the present invention is designed to allow a center on alower side of a hub 120 to be pivoted in both radial and thrustdirections through a ball bearing 150 coming into direct contact withthe lower portion of the hub, so that the hub can be rotated whilemaintaining a rotational center without mechanical contact between thehub 120 and an aerodynamic bearing 140 resulting in noise and startingfailure caused by rotation of the hub 120 during an initial starting (orlow-speed rotation) of the spindle motor 100.

That is, the spindle motor 100 for hard disk drives according to thepresent invention is designed so that the hub 120 is supported in apoint-contact manner as a whirligig and operates on the principle ofrotation of the whirligig (The faster a whirligig rotates, the morerotational inertia increases. Therefore, a whirligig rotating at a highspeed tends to rotate more easily than that at a low speed. Thisphenomenon is derived from the law of conservation of angularmomentum.), thus improving rotational rigidity of the bearing againstdisturbance as well as its capability of rotating without a slant. Thespindle motor 100 can thus obtain a high rotation precision.

Further, the spindle motor 100 for hard disk drives according to thepresent invention is designed so that when the hub 120 rotates at a highspeed, aerodynamic pressure is established between the aerodynamicbearing 140 in which a main bearing body 142 is provided with at leastone air groove 142 a, and the hub 120, thus coping with thrust load ofthe hub 120 and not causing the hub 120 to be in contact with the mainbearing body 142 while the hub 120 is rotating at a high speed.

As mentioned above, the spindle motor 100 for hard disk drives accordingto the present invention is characterized by a construction combiningthe aerodynamic bearing 140 with the ball bearing 150, and by aconstruction causing the hub 120 to be supported in a point-contactmanner the same as a whirligig in rotation.

The spindle motor 100 for hard disk drives according to the presentinvention, comprises a base 110; a hub 120 fitted rotatably on the base110 and having a platter (not shown) mounted on the hub; a stator 130constructed in such a manner that an open press-fit portion 132 isprovided at a center portion thereof and that at least one coil 136 iswound around a plurality of cores 134, which are formed at the sameangular distance along an outer circumference of the stator; anaerodynamic bearing 140 including a disk-shaped main bearing body 142formed with at least one air groove 142 a so as to generate aerodynamicpressure in cooperation with the hub 120, and an auxiliary bearing body144, formed integrally on the lower portion of the main bearing body 142so as to mount on the base 100 through the open press-fit portion 132 ofthe stator 130; a ball bearing 150 for causing the rotational center ofthe hub 120 to be rotatably supported on the center of the aerodynamicbearing 140; and an annular permanent magnet 160, fitted on an innercircumferential surface of the hub 120 adjacent to the cores 134 aroundwhich the coil 136 of the stator 130 is wound, for generating drivingforce for rotating the hub 120 by means of a magnetic field establishedin cooperation with the coil 136.

When power is supplied to the spindle motor 100 for hard disk drivesaccording to the present invention, a magnetic field is establishedbetween the cores 134 wound around by the coil 136 of the stator 130 andthe permanent magnet 160. Then, the hub 120 rotates about the ballbearing 150. Once the hub 120 rotates, air begins to flow between thehub 120 and the aerodynamic bearing 140, thus forming a layer of air.Most of the load to which this air layer is subjected is thrust load ina non-contact state.

Description will be made in detail below regarding construction of thespindle motor 100 for hard disk drives according to the presentinvention. First, as shown in FIGS. 4 to 8, the base 110 serves as alower portion of the spindle motor 100. The base 100 is provided with aseating recess 112 (FIG. 4), which is formed in a concentric concaveshape and to a predetermined depth. That is, the concentric seatingrecess 112 is formed on an upper portion of the base 110 to apredetermined depth.

The base 100, constructed as mentioned above, is provided with thestator 130 and the aerodynamic bearing 140 in a space between theseating recess 112 and the hub 120 rotatably fitted above the base 110.The stator 130 and the aerodynamic bearing 140 will be described below.

The hub 120 rotates by means of a magnetic field established between thecoil 136 of the stator 130 and the permanent magnet 160. As shown inFIGS. 4 and 8, the hub 120 is provided with a lower cylindrical section122 formed with an open lower portion and positioned in the seatingrecess 112 of the base 110, and a platter mounting section 124integrally formed on the cylindrical section 122 and mounted with aplatter (not shown) called a magnetic disk. Here, the cylindricalsection 122 has a smaller outer diameter than the seating recess 112 ofthe base 110, while the cylindrical section 122 has a larger innerdiameter than an outer diameter of the main bearing body 142 of theaerodynamic bearing 140.

The hub 120, constructed as above, is fitted in such a way that thecylindrical section 122 is rotatably positioned in the seating recess112 of the base 110, without generating mechanical contact between anouter circumferential surface of the cylindrical section 122 and aninner circumferential surface of the seating recess 112, between a lowersurface of the cylindrical section 122 and a bottom surface of theseating recess 112, or between an inner circumferential surface of thecylindrical section 122 and an outer circumferential surface of the mainbearing body 142 of the aerodynamic bearing 140.

Meanwhile, the hub 120 is provided with a spindle shaft 126, whichdownwardly extends from the lower surface of the hub 120, i.e., a lowersurface of a transition between the platter mounting section and thecylindrical section 122 in a conical form. The spindle shaft 126 isinserted into an inner race of the ball bearing 150. The plattermounting section 124 belonging to the upper portion of the hub 120 isprovided with a cavity 124 a open in an upward direction, so as toreduce the total weight of the hub 120 as much as possible.

The stator 130 functions to generate a driving force for rotating thehub 120 through a magnetic field, which is established in cooperationwith the permanent magnet 160 by a power supply. The stator 130 isfixedly mounted on the auxiliary bearing body 144 of the aerodynamicbearing 140. Therefore, the stator 130 is arranged in the space betweenthe seating recess 112 of the base 110 and the cylindrical section 120of the hub 120, together with the aerodynamic bearing 140.

The construction of the stator 130, as mentioned above, is provided witha vertically open press-fit portion 132 at the center thereof, andincludes a plurality of magnetically inducible cores 134 integrallyformed along an outer circumference of the stator at the same angulardistance, and a coil 136 wound around each core 134 and establishing amagnetic field in cooperation with the permanent magnet 160 by supplyingpower to convert each core 134 into an electromagnet.

The stator 130 constructed as mentioned above is not seated in theseating recess 112 of the base 110 by itself, but is positioned in thespace between the seating recess 112 of the base 110 and the cylindricalsection 122 of the hub 120 after it is firmly fitted on the outercircumferential surface of the auxiliary bearing body 144 of theaerodynamic bearing 140.

The aerodynamic bearing 140 is arranged in the space between the base110 and the hub 120, establishing aerodynamic pressure in cooperationwith the lower surface of the hub 120 while the hub 120 rotates. Theaerodynamic bearing 140 includes a disk-shaped main bearing body 142formed with at least one air groove 142 a on the upper surface and/orthe outer circumferential surface thereof, and an auxiliary bearing body144 integrally formed on the lower portion of the main bearing body 142and fixedly fitted in the seating recess 112 of the base 110 through theopen press-fit portion 132 a of the stator 130 within the space betweenthe base 110 and the hub 120.

The aerodynamic bearing 140 is fixedly supported in the seating recess112 of the base 110, as follows: First, the auxiliary bearing body 144of the aerodynamic bearing 140 is press-fitted into the open press-fitportion 132 of the stator 130 so as to fix the stator 130 on the outercircumferential surface of the auxiliary bearing body 144, andsequentially a bottom surface of the auxiliary bearing body 144 isfirmly seated on a bottom surface of the seating recess 112 of the base110, all being concentrically arranged with respect to each other.

The main bearing body 142 of the aerodynamic bearing 140 as mentionedabove has a smaller outer diameter than an inner diameter of thecylindrical section 122 of the hub 120, so that the main bearing body142 can be fitted so as not to allow contact with the innercircumferential surface of the cylindrical section 122 of the hub 120.Further, the main bearing body 142 of the aerodynamic bearing 140 isfitted so as not to allow the upper surface of the main bearing body 142to come into contact with the lower surface of the hub 120.

Meanwhile, the air groove 142 a, which is formed on the main bearingbody 142 of the aerodynamic bearing 140, may be formed on the uppersurface of the main bearing body 142 and/or on the outer circumferentialsurface of the main bearing body 142. It is preferred that the airgroove 142 a is concentrically formed on the upper surface of the mainbearing body 142 and/or that the air groove 142 a is mono-directionallyformed on the outer circumferential surface of the main bearing body142.

The ball bearing 150 is used to allow the spindle shaft 126 of the hub120 to be rotatably supported at the center of the aerodynamic bearing140. As shown in FIGS. 4 to 8, the ball bearing 150 is fixedly supportedin a central through-hole 146, which passes through the rotationalcenter of the aerodynamic bearing 140, in particular of the auxiliarybearing body 144 of the aerodynamic bearing 140.

The spindle shaft 126 projected from the lower surface of the hub 120 isinserted into an inner race of the ball bearing 150. In other words, thespindle shaft 126 of the hub 120 is pivoted in both radial and thrustdirections by the ball bearing 150, which comes into direct contact witha lower center of the hub 120, so that during an initial starting (orlow-speed rotation) of the spindle motor 100, mechanical contactresulting in starting failure or noise accompanying rotation of the hub120 is no longer generated between the hub 120 and the aerodynamicbearing 140.

As mentioned above, during an initial starting of the spindle motor 100(during a low-speed rotation), the spindle shaft 126 of the hub 120 iscompensatively supported by the ball bearing 150 in both radial andthrust directions, so that mechanical contact resulting in startingfailure or noise accompanying rotation of the hub 120 is not generatedbetween the hub 120 and the aerodynamic bearing 140. As a result, thehub 120 is capable of rotating without deviating from its rotationalcenter.

In contrast, during a high-speed rotation of the spindle motor 100,aerodynamic pressure, which is established between the hub 120 and theaerodynamic bearing 140 through the air groove 142 a of the aerodynamicbearing 140, allows most of the thrust load of the hub 120 to besupported on the aerodynamic bearing 140, so that the rotationalrigidity of the ball bearing 150 against external disturbance as well asthe capability of the hub 120 to rotate without a slant is improved.Therefore, the spindle motor 100 is capable of maintaining a highrotational precision. As a result, it is possible for the spindle motor100 of the present invention to rotate at a high speed even though theball bearing 150 is employed to the spindle motor. That is, when the hub120 rotates at a low speed, the ball bearing 150 compensatively supportsthe spindle shaft 126 of the hub 120 in both radial and thrustdirections so that the ball bearing 150 is subjected to radial andthrust loads from the hub 120. In contrast, when the hub 120 rotates ata high speed, the aerodynamic bearing 140 supports most of the radialand thrust loads from the hub 120 so that the ball bearing 150 issubjected to a slight level of thrust load from the hub 120, whichenables the spindle motor 100 to be rotated at a high speed.

Further, the aforementioned ball bearing 150 is provided at a lowerposition than the main bearing body 142 of the aerodynamic bearing 140,in particular in the auxiliary bearing body 144, and thus the ballbearing 150 has a rotational supporting point located under the mainbearing body 142.

The permanent magnet 160 generates a driving force for rotating the hub120 by means of magnetic field, which is established between the coil134 of the stator 130 and the permanent magnet 160 by supplying power.The permanent magnet 160 is fitted on the inner circumferential surfaceof the hub 120 adjacent to the cores 134, around which the coil 136 ofthe stator 130 is wound. Therefore, the magnetic field is establishedbetween the permanent magnet 160 and the coil 136.

The permanent magnet 160 has an annular ring shape and has a sizecompatible with the inner diameter of the cylindrical section 122 of thehub 120. So, the permanent magnet 160 is fixedly fitted on the innercircumferential surface of the cylindrical section 122 of the hub 120,which faces toward the cores 134 of the stator 130.

As mentioned above, since the permanent magnet 160 is fixedly fitted onthe inner circumferential surface of the cylindrical section 122 of thehub 120, the magnetic field is established between the permanent magnet160 and the coil 134 of the stator 130 by supplying power, thus rotatingthe hub 120 in one direction.

In brief, the spindle motor 100 for hard disk drives according to thepresent invention is designed so that when the hub 120 rotates at a lowspeed, mechanical contacts resulting in starting failure and noiseaccompanying rotation of the hub 120 is no longer generated between thehub 120 and the aerodynamic bearing 140, by compensatively supportingthe hub 120 in both radial and thrust directions through the ballbearing 150, and when the hub 120 rotates at a high speed, most of thethrust load of the hub 120 is supported on the aerodynamic bearing 140by establishing aerodynamic pressure between the hub 120 and theaerodynamic bearing 140 through the air groove 142 a of the aerodynamicbearing 140. Therefore, the spindle motor 100 is capable of improvingthe rotational rigidity of the ball bearing 150 against externaldisturbance as well as the capability of the hub 120 to rotate without aslant, thereby allowing maintenance of a high rotational precision.

Further, the spindle motor 100 for hard disk drives according to thepresent invention can be constructed so that the ball bearing 150 forrotatably supporting the hub 120 is provided at a lower position than anupper horizontal plane of the main bearing body 142 of the aerodynamicbearing 140, as shown in FIG. 7, so that the ball bearing 150 has arotatable supporting point under the upper horizontal plane of the mainbearing body 142 of the aerodynamic bearing 140.

Here, in order to rotatably mount the hub 120 at the center of theaerodynamic bearing 140 by aid of the ball bearing 150, the ball bearing150 is fitted in a thrust or vertical direction into the centralthrough-hole 146, which is located under the upper horizontal plane ofthe main bearing body 142 of the aerodynamic bearing 140 and which isopened vertically at the center of the aerodynamic bearing 140. Further,the spindle shaft 126, which extends downwardly from the lower surfaceof the hub 120 to take a conical shape, is press-fitted into the innerrace of the ball bearing 150. Description will be made regarding variousconstructions in which the ball bearing 150 for rotatably supporting thehub 120 can be mounted at different positions.

FIG. 9 is a cross-sectional view of a spindle motor for hard disk driveswith a pivot structure according to one embodiment of the presentinvention, and FIG. 10 is a cross-sectional view showing a spindle motorfor hard disk drives with a pivot structure according to anotherembodiment of the present invention.

First, as shown in FIG. 9, a spindle motor 200 for hard disk drivesaccording to the present invention may be designed to mount a ballbearing 250 for rotatably supporting a hub 220 at a first position,wherein the ball bearing 250 is mounted at the rotational center of thehub 220 flush with an upper horizontal plane of a main bearing body 242of an aerodynamic bearing 240, and thus the ball bearing 250 has arotatable supporting point flush with the upper horizontal plane of themain bearing body 242.

As mentioned above, in order to make the rotatable supporting point ofthe ball bearing 250 flush with the upper horizontal plane of the mainbearing body 242, the hub 220 is provided with a central through-hole226, which is formed to pass through the center of the hub 220 in avertical direction. Further, the ball bearing 250 is fitted in a thrustor vertical direction into the central through-hole 226, until the ballbearing 250 is flush with the upper horizontal plane of the main bearingbody 242 of aerodynamic bearing 240. Finally, the aerodynamic bearing240 is formed with a upward supporting shaft 246 at the center of theupper surface thereof, and then the supporting shaft 246 is press-fittedinto an inner race of the ball bearing 250.

Of course, the spindle motor 200 for hard disk drives shown in FIG. 9 issimilar to the spindle motor 100 for hard disk drives shown in FIGS. 4to 8, in that the combination of the ball bearing 250 with theaerodynamic bearing 240 is made to enable the hub 220 to follow thepoint-contact supporting construction on the basis of the rotationalprinciple of the whirligig. However, the difference between them isdependent on a position where the ball bearing 250 is mounted.

Meanwhile, as shown in FIG. 10, a spindle motor 300 for hard disk drivesaccording to the present invention may be designed to mount a ballbearing 350 for rotatably supporting a hub 320 at a second position,wherein the ball bearing 350 is mounted at an upper center of the hub320 at a higher position than an upper horizontal plane of a mainbearing body 342 of an aerodynamic bearing 340, and thus the ballbearing 350 has a rotatable supporting point at the higher position thanthe upper horizontal plane of the main bearing body 342 of theaerodynamic bearing 340.

As mentioned above, in order to provide the rotatable supporting pointof the ball bearing 350 at a higher position than the upper horizontalplane of the main bearing body 342 of the aerodynamic bearing 340, thehub 320 is provided with a central through-hole 326, which is formed topass through the center of the hub 320 in a vertical direction. Further,the ball bearing 350 is fitted in a thrust or vertical direction intothe central through-hole 326 so that the ball bearing 350 is positionedat a higher position than the upper horizontal plane of the main bearingbody 342 of the aerodynamic bearing 340. Finally, the aerodynamicbearing 340 is formed with a upward long supporting shaft 346 at thecenter of the upper surface thereof, and then the supporting shaft 346is press-fitted into an inner race of the ball bearing 350.

Similarly, the spindle motor 300 for hard disk drives shown in FIG. 10is similar to the spindle motor 100 for hard disk drives shown in FIGS.4 to 8 and to the spindle motor 200 for hard disk drives shown in FIG.9, in that combination of the ball bearing 350 with the aerodynamicbearing 340 is made to enable the hub 320 to follow the point-contactsupporting construction on the basis of the rotational principle of thewhirligig. However, the difference among them is dependent on a positionwhere the ball bearing 350 is mounted.

FIG. 11 is a perspective view of a second embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention, FIG. 12 is a perspective view of a thirdembodiment for an aerodynamic bearing assembly of a spindle motor with apivot structure according to the present invention, FIG. 13 is aperspective view of a fourth embodiment for an aerodynamic bearingassembly of a spindle motor with a pivot structure according to thepresent invention, FIG. 14 is a perspective view of a fifth embodimentfor an aerodynamic bearing assembly of a spindle motor with a pivotstructure according to the present invention, FIG. 15 is a perspectiveview of a sixth embodiment for an aerodynamic bearing assembly of aspindle motor with a pivot structure according to the present invention,FIG. 16 is a perspective view of a seventh embodiment for an aerodynamicbearing assembly of a spindle motor with a pivot structure according tothe present invention, and FIG. 17 is a perspective view of a eighthembodiment for an aerodynamic bearing assembly of a spindle motor with apivot structure according to the present invention.

FIGS. 11 to 17 illustrate various embodiments for an aerodynamic bearingassembly. First, FIG. 11 shows a construction in that an air groove 142b is provided on an outer circumferential surface of a main bearing body142 of an aerodynamic bearing 140.

The air groove 142 b as shown in FIG. 11 is formed on the outercircumferential surface of the main bearing body 142 instead of theupper horizontal surface of the main bearing body 142 of the aerodynamicbearing 140 as shown in FIG. 8, so that aerodynamic pressure isgenerated between the outer circumferential surface of the main bearingbody 142 and the inner circumferential surface of a cylindrical section122, which is formed on an lower portion of the hub 120, while the hub120 rotates. That is, the embodiment in FIG. 11 is a construction inwhich of an upper horizontal surface of the main bearing body 142 of theaerodynamic bearing 140, an outer circumferential surface of the mainbearing body 142 of the aerodynamic bearing 140, a lower horizontalsurface of the hub 120 and a lower inner circumferential surface of thehub 120, only the outer circumferential surface of the main bearing body142 of the aerodynamic bearing 140 is provided with the air groove 142b.

By contrast, FIG. 12 shows a construction in which of an upperhorizontal surface of the main bearing body 142 of the aerodynamicbearing 140, an outer circumferential surface of the main bearing body142 of the aerodynamic bearing 140, a lower horizontal surface of thehub 120 and a lower inner circumferential surface of the hub 120, boththe upper horizontal surface and the outer circumferential surface ofthe main bearing body 142 of the aerodynamic bearing 140 are providedwith air grooves 142 a and 142 b, respectively. The air grooves 142 aand 142 b, which are formed on the upper horizontal surface and theouter circumferential surface of the main bearing body 142 of theaerodynamic bearing 140, cause aerodynamic pressure to be generatedbetween the upper horizontal surface of the main bearing body 142 andthe lower horizontal surface of the cylindrical section 122 of the hub120 as well as between the outer circumferential surface of the mainbearing body 142 and the inner circumferential surface of thecylindrical section 122 of the hub 120, while the hub 120 rotates.

Further, FIG. 13 shows a construction in which of an upper horizontalsurface of the main bearing body 142 of the aerodynamic bearing 140, anouter circumferential surface of the main bearing body 142 of theaerodynamic bearing 140, a lower horizontal surface of the hub 120 and alower inner circumferential surface of the hub 120, the lower horizontalsurface of the hub 120 or a lower horizontal surface of a transitionbetween the cylindrical section 122 and a platter mounting section 124is provided with an air groove 122 a. Here, it should be noted that suchan air groove is not formed on the aerodynamic bearing 140. The airgroove 122 a, which is formed on the lower horizontal surface of the hub120, causes aerodynamic pressure to be generated between the upperhorizontal surface of the main bearing body 142 of the aerodynamicbearing 140 and the lower horizontal surface of the hub 120, while thehub 120 rotates.

FIG. 14 shows a construction in which of an upper horizontal surface ofthe main bearing body 142 of the aerodynamic bearing 140, an outercircumferential surface of the main bearing body 142 of the aerodynamicbearing 140, a lower horizontal surface of the hub 120 and a lower innercircumferential surface of the hub 120, the lower inner circumferentialsurface of the hub 120 is provided with an air groove 122 b. Here, itshould be also noted that such an air groove is not formed on theaerodynamic bearing 140. Therefore, the air groove 122 b, which isformed on the lower inner circumferential surface of the hub 120, causesaerodynamic pressure to be generated between the outer circumferentialsurface of the main bearing body 142 of the aerodynamic bearing 140 andthe lower inner circumferential surface of the hub 120, while the hub120 rotates.

FIG. 15 shows a construction in which two among an upper horizontalsurface of the main bearing body 142 of the aerodynamic bearing 140, anouter circumferential surface of the main bearing body 142 of theaerodynamic bearing 140, a lower horizontal surface of the hub 120 and alower inner circumferential surface of the hub 120, e.g., both the lowerhorizontal surface of the hub 120 and the lower inner circumferentialsurface of the hub 120, are provided with air grooves 122 a and 122 b,respectively. Here, it should be also noted that such air grooves arenot formed on the aerodynamic bearing 140. The air grooves 122 a and 122b, which are formed on the lower horizontal surface and the lower innercircumferential surface of the hub 120, cause aerodynamic pressure to begenerated between the outer circumferential surface of the main bearingbody 142 of the aerodynamic bearing 140 and the lower innercircumferential surface of the hub 120 as well as between the outercircumferential surface of the main bearing body 142 and the lower innercircumferential surface of the hub 120, while the hub 120 rotates.

FIG. 16 shows a construction in which of an upper horizontal surface ofthe main bearing body 142 of the aerodynamic bearing 140, an outercircumferential surface of the main bearing body 142 of the aerodynamicbearing 140, a lower horizontal surface of the hub 120 and a lower innercircumferential surface of the hub 120, both the upper horizontalsurface of the main bearing body 142 of the aerodynamic bearing 140 andthe lower inner circumferential surface of the hub 120 are provided withair grooves 142 a and 122 b, respectively. Therefore, the air grooves122 a and 122 b, which are formed on the upper horizontal surface of themain bearing body 142 of the aerodynamic bearing 140 and the lower innercircumferential surface of the hub 120, cause aerodynamic pressure to begenerated between the upper horizontal surface of the main bearing body142 of the aerodynamic bearing 140 and the lower horizontal surface ofthe hub 120 as well as between the outer circumferential surface of themain bearing body 142 and the lower inner circumferential surface of thehub 120, while the hub 120 rotates.

FIG. 17 shows a construction in which of an upper horizontal surface ofthe main bearing body 142 of the aerodynamic bearing 140, an outercircumferential surface of the main bearing body 142 of the aerodynamicbearing 140, a lower horizontal surface of the hub 120 and a lower innercircumferential surface of the hub 120, both the outer circumferentialsurface of the main bearing body 142 of the aerodynamic bearing 140 andthe lower horizontal surface of the hub 120 are provided with airgrooves 142 b and 122 a, respectively. Therefore, the air grooves 142 aand 122 a, which are formed on the outer circumferential surface of themain bearing body 142 of the aerodynamic bearing 140 and the lowerhorizontal surface of the hub 120, cause aerodynamic pressure to begenerated between the outer circumferential surface of the main bearingbody 142 of the aerodynamic bearing 140 and the lower innercircumferential surface of the hub 120 as well as between the upperhorizontal surface of the main bearing body 142 and the lower horizontalsurface of the hub 120, while the hub 120 rotates.

The construction of the air groove(s) for implementing each embodimentshown in FIGS. 1 to 17, as mentioned above, is different from that shownin FIGS. 1 to 8, but its operation shown in FIGS. 1 to 17 is the same asthat shown in FIGS. 1 to 8.

FIG. 18 is a cross-sectional view of a ninth embodiment for anaerodynamic bearing assembly of a spindle motor with a pivot structureaccording to the present invention, FIG. 19 is a cross-sectional view ofa tenth embodiment for an aerodynamic bearing assembly of a spindlemotor with a pivot structure according to the present invention, andFIG. 20 is a cross-sectional view of an eleventh embodiment for anaerodynamic bearing assembly of a spindle motor with a pivot structureaccording to the present invention.

In FIGS. 18 to 20, there is shown a construction for minimizing frictionbetween a lower horizontal surface of a hub 120 and an upper horizontalsurface of a main bearing body 142 of the aerodynamic bearing 140 duringan initial starting. First, as shown in FIG. 18, the upper horizontalsurface of the main bearing body 142 of the aerodynamic bearing 140 isprovided with an oilless bearing 170, which takes a ring shape.

The oilless bearing 170 constructed, as mentioned above, is mounted onthe upper horizontal surface of the main bearing body 142 and is spacedapart from the lower horizontal surface of the hub 120 by apredetermined interval, so that friction between the lower horizontalsurface of the hub 120 and the upper horizontal surface of the mainbearing body 142 is minimized by preventing the hub 120 from beingdeclined during an initial starting of the spindle motor 100. In thisway, by prevention of the declination of the hub 120 and thus minimizingthe friction between the lower horizontal surface of the hub 120 and theupper horizontal surface of the main bearing body 142, mechanicalcontact resulting in noise and starting failure can be eliminated.

Further, the oilless bearing 170 mounted on the upper horizontal surfaceof the main bearing body 142 of the aerodynamic bearing 140 may beprovided with an air groove 170-1, for example on the upper surface ofthe oilless bearing facing to the lower horizontal surface of the hub120.

It goes without saying that the oilless bearing 170 shown in FIG. 18 maybe employed in the spindle motor in which the upper horizontal surfaceof the main bearing body 142 of the aerodynamic bearing 140 is providedwith the air groove 142 a shown in FIG. 8, or in the spindle motor 100in which the outer circumferential surface of the main bearing body 142of the aerodynamic bearing 140 is provided with the air groove 142 bshown in FIG. 11, or in the spindle motor 100 in which both the upperhorizontal surface and the outer circumferential surface of the mainbearing body 142 of the aerodynamic bearing 140 are provided with theair grooves 142 a and 142 b, respectively, shown in FIG. 12.

Similarly, it is natural that the oilless bearing 170 shown in FIG. 18may be employed in the spindle motor 100 in which the lower horizontalsurface of the hub 120 is provided with the air groove 122 a shown inFIG. 13, or in the spindle motor 100 in which the inner circumferentialsurface of the cylindrical section 122 of the hub 120 is provided withthe air groove 122 b shown in FIG. 14, or in the spindle motor 100 inwhich both the lower horizontal surface of the hub 120 and the innercircumferential surface of the cylindrical section 122 of the hub 120are provided with the air grooves 122 a and 122 b, respectively, shownin FIG. 15, or in the spindle motor 100 in which both the upperhorizontal surface of the main bearing body 142 of the aerodynamicbearing 140 and the inner circumferential surface of the cylindricalsection 122 of the hub 120 are provided with the air grooves 142 a and122 b, respectively, shown in FIG. 16, or in the spindle motor 100 inwhich both the outer circumferential surface of the main bearing body142 of the aerodynamic bearing 140 and the lower horizontal surface ofthe hub 120 are provided with the air grooves 142 b and 122 a,respectively, shown in FIG. 17.

FIG. 19 shows a construction in which the lower horizontal surface ofthe hub 120 is provided with an oilless bearing 170 a in a ring shape,unlike the construction of FIG. 18 in which the upper horizontal surfaceof the main bearing body 142 of the aerodynamic bearing 140 is providedwith an oilless bearing 170 in a ring shape. This oilless bearing 170 a,constructed as mentioned above, is mounted on the lower horizontalsurface of the hub 120 and is spaced apart from the upper horizontalsurface of the main bearing body 142 at a predetermined interval, sothat friction between the lower horizontal surface of the hub 120 andthe upper horizontal surface of the main bearing body 142 is minimizedby preventing the hub 120 from being declined during an initial startingof the spindle motor 100. In this way, by prevention of the declinationof the hub 120 and thus minimizing the friction between the lowerhorizontal surface of the hub 120 and the upper horizontal surface ofthe main bearing body 142, mechanical contact resulting in noise andstarting failure can be eliminated. Here, the oilless bearing 170 amounted on the lower horizontal surface of the hub 120 may be providedwith an air groove 170 a-1, for example on the lower surface of theoilless bearing facing to the upper horizontal surface of the mainbearing body 142 of the aerodynamic bearing 140.

Meanwhile, the oilless bearing 170 a mounted on the lower horizontalsurface of the hub 120, as shown in FIG. 19, may be employed in thespindle motor in which the upper horizontal surface of the main bearingbody 142 of the aerodynamic bearing 140 is provided with the air groove142 a as shown in FIG. 8, or in the spindle motor 100 in which the outercircumferential surface of the main bearing body 142 of the aerodynamicbearing 140 is provided with the air groove 142 b as shown in FIG. 11,or in the spindle motor 100 in which both the upper horizontal surfaceand the outer circumferential surface of the main bearing body 142 ofthe aerodynamic bearing 140 are provided with the air grooves 142 a and142 b, respectively, as shown in FIG. 12.

Similarly, it will be apparent to those in the art that the oillessbearing 170 a mounted on the lower horizontal surface of the hub 120 asshown in FIG. 19 may be employed in the spindle motor 100 in which thelower horizontal surface of the hub 120 is provided with the air groove122 a, as shown in FIG. 13, or in the spindle motor 100 in which theinner circumferential surface of the cylindrical section 122 of the hub120 is provided with the air groove 122 b, as shown in FIG. 14, or inthe spindle motor 100 in which both the lower horizontal surface of thehub 120 and the inner circumferential surface of the cylindrical section122 of the hub 120 are provided with the air grooves 122 a and 122 b,respectively, as shown in FIG. 15, or in the spindle motor 100 in whichboth the upper horizontal surface of the main bearing body 142 of theaerodynamic bearing 140 and the inner circumferential surface of thecylindrical section 122 of the hub 120 are provided with the air grooves142 a and 122 b, respectively, as shown in FIG. 16, or in the spindlemotor 100 in which both the outer circumferential surface of the mainbearing body 142 of the aerodynamic bearing 140 and the lower horizontalsurface of the hub 120 are provided with the air grooves 142 b and 122a, respectively, as shown in FIG. 17.

FIG. 20 shows a construction in which both the upper horizontal surfaceof the main bearing body 142 of the aerodynamic bearing 140 and thelower horizontal surface of the hub 120 are provided with oillessbearings 170 and 170 a opposite to each other in a ring shape. Theseoilless bearings 170 and 170 a are spaced apart from each other at apredetermined interval, so that friction between the lower horizontalsurface of the hub 120 and the upper horizontal surface of the mainbearing body 142 is minimized by preventing the hub 120 from beingdeclined during an initial starting of the spindle motor 100.Consequently, by prevention of the declination of the hub 120 and theresulting minimization of the friction between the lower horizontalsurface of the hub 120 and the upper horizontal surface of the mainbearing body 142, mechanical contact resulting in noise and startingfailure can be eliminated.

Here, any one of two oilless bearings 170 and 170 a may be provided withan air groove 170-1 or 170 a-1. For example, the air groove 170-1 may beformed on the upper surface of the oilless bearing 170, which is mountedon the upper horizontal surface of the main bearing body 142 of theaerodynamic bearing 140, or the air groove 170 a-1 may be formed on thelower surface of the oilless bearing facing 170 a, which is mounted onthe lower horizontal surface of the hub 120.

Meanwhile, these oilless bearings 170 and 170 a as shown in FIG. 20 maybe also employed in the spindle motor 100 in which the upper horizontalsurface of the main bearing body 142 of the aerodynamic bearing 140 isprovided with the air groove 142 a as shown in FIG. 8, or in the spindlemotor 100 in which the outer circumferential surface of the main bearingbody 142 of the aerodynamic bearing 140 is provided with the air groove142 b, as shown in FIG. 11, or in the spindle motor 100 in which boththe upper horizontal surface and the outer circumferential surface ofthe main bearing body 142 of the aerodynamic bearing 140 are providedwith the air grooves 142 a and 142 b, respectively, as shown in FIG. 12.

Similarly, it will be easily understood to those in the art that theoilless bearings 170 and 170 a may be employed in the spindle motor 100in which the lower horizontal surface of the hub 120 is provided withthe air groove 122 a, as shown in FIG. 13, or in the spindle motor 100in which the inner circumferential surface of the cylindrical section122 of the hub 120 is provided with the air groove 122 b, as shown inFIG. 14, or in the spindle motor 100 in which both the lower horizontalsurface of the hub 120 and the inner circumferential surface of thecylindrical section 122 of the hub 120 are provided with the air grooves122 a and 122 b, respectively, as shown in FIG. 15, or in the spindlemotor 100 in which both the upper horizontal surface of the main bearingbody 142 of the aerodynamic bearing 140 and the inner circumferentialsurface of the cylindrical section 122 of the hub 120 are provided withthe air grooves 142 a and 122 b, respectively, as shown in FIG. 16, orin the spindle motor 100 in which both the outer circumferential surfaceof the main bearing body 142 of the aerodynamic bearing 140 and thelower horizontal surface of the hub 120 are provided with the airgrooves 142 b and 122 a, respectively, as shown in FIG. 17.

According to the present invention as mentioned above, the hub, arotatable object, of the spindle motor for hard disk drives is not onlypivoted in both radial and thrust directions by the ball bearing, whichcomes into direct contact with the center of the hub, so as to performrotation according to the rotational principle of the whirligig, butalso is subjected to the thrust load through the aerodynamic bearingassembly with the air groove(s) without being in contact with it, sothat mechanical contacts resulting in noise and starting failure of theaerodynamic bearing assembly and/or the hub can be prevented during aninitial starting (during a low-speed rotation), and thus the hub canmaintain an excellent rotational precision.

While this invention has been described in connection with what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not limited to thedisclosed embodiment and the drawings, but, on the contrary, it isintended to cover various modifications and variations within the spiritand scope of the appended claims.

According to the present invention as mentioned above, the rotatable hubof the spindle motor for hard disk drives is designed not only to bepivoted in both radial and thrust directions by the ball bearing, whichcomes into direct contact with the center of the hub, so as to performrotation according to the rotational principle of the whirligig, butalso to be subjected to the thrust load through the aerodynamic bearingassembly with the air groove(s) without being in contact with it, sothat the hub can maintain a rotational center without mechanical contactresulting in noise and starting failure of the aerodynamic bearingassembly during an initial starting (during low-speed rotation).

Further, according to the present invention as mentioned above, the hub,which is designed to have a conical structure like a whirligig and thusto have a rotatable point-contact supporting structure through the ballbearing is combined with the aerodynamic bearing with at least one airgroove, which is formed on at least one of the upper horizontal surfaceof the main bearing body of the aerodynamic bearing, the outercircumferential surface of the main bearing body of the aerodynamicbearing, the lower horizontal surface of the hub and the innercircumferential surface of the cylindrical section of the hub, so thatrotational rigidity of the bearing against disturbance as well as itscapability of rotating without a slant is improved, and thus anexcellent rotational precision can be obtained.

In addition, according to the present invention, the hub is designed tohave a conical structure like a whirligig and thus to have a rotatablepoint-contact supporting structure through the ball bearing, so thateven though static electricity is generated by friction between the aircaused by a high-speed rotation and the platter, the static electricitycan be discharged through the ball bearing. Therefore, structural safetyof the spindle motor can be improved.

1. An aerodynamic bearing assembly employed in a spindle motor for harddisk drives, the spindle motor including a base, a hub, a stator and apermanent magnet, the base serving as a lower portion of the spindlemotor, the hub being rotatably fitted on the base and able to fixedlymount a platter, the stator being formed with a plurality of cores woundaround by at least one coil along an outer circumference of the statorand being formed with an open press-fit portion at a center of thestator, the permanent magnet being fitted on an inner circumferentialsurface of the hub and generating a magnetic field in cooperation withthe coil, the aerodynamic bearing assembly comprising: an aerodynamicbearing including a main bearing body formed in a concentric disk shapeto serve as an upper portion of the aerodynamic bearing, and anauxiliary bearing body integrally formed on a lower portion of the mainbearing body and press-fitted into an open press-fit portion of thestator to fixedly mount the stator on an outer circumferential surfaceof the auxiliary bearing body, the aerodynamic bearing being fixedlyinstalled in a space between the base and the hub; and a ball bearingfor rotatably pivoting a center of the hub in both radial and thrustdirections at an center of the aerodynamic bearing, wherein at least oneof an upper horizontal surface of the main bearing body of theaerodynamic bearing, an outer circumferential surface of the mainbearing body of the aerodynamic bearing, a lower horizontal surface ofthe hub and a lower inner circumferential surface of the hub, isprovided with at least one air groove having a predetermined depth, theair groove generating aerodynamic pressure between the hub and theaerodynamic bearing while the hub rotates.
 2. An aerodynamic bearingassembly as claimed in claim 1, wherein the air groove is formed on theupper horizontal surface of the main bearing body of the aerodynamicbearing to generate aerodynamic pressure between the lower horizontalsurface of the hub and the upper horizontal surface of the main bearingbody of the aerodynamic bearing.
 3. An aerodynamic bearing assembly asclaimed in claim 1, wherein the air groove is formed on the outercircumferential surface of the main bearing body of the aerodynamicbearing to generate aerodynamic pressure between the lower innercircumferential surface of the hub and the outer circumferential surfaceof the main bearing body of the aerodynamic bearing.
 4. An aerodynamicbearing assembly as claimed in claim 1, wherein the air groove is formedboth on the upper horizontal surface of the main bearing body of theaerodynamic bearing and on the outer circumferential surface of the mainbearing body of the aerodynamic bearing to generate aerodynamic pressurebetween the lower horizontal surface of the hub and the upper horizontalsurface of the main bearing body of the aerodynamic bearing and betweenthe lower inner circumferential surface of the hub and the outercircumferential surface of the main bearing body of the aerodynamicbearing.
 5. An aerodynamic bearing assembly as claimed in claim 1,wherein the air groove is formed on the lower horizontal surface of thehub to generate aerodynamic pressure between the lower horizontalsurface of the hub and the upper horizontal surface of the main bearingbody of the aerodynamic bearing.
 6. An aerodynamic bearing assembly asclaimed in claim 1, wherein the air groove is formed on the lower innercircumferential surface of the hub to generate aerodynamic pressurebetween the lower inner circumferential surface of the hub and the outercircumferential surface of the main bearing body of the aerodynamicbearing.
 7. An aerodynamic bearing assembly as claimed in claim 1,wherein the air groove is formed both on the lower horizontal surface ofthe hub and on the lower inner circumferential surface of the hub togenerate aerodynamic pressure between the lower horizontal surface ofthe hub and the upper horizontal surface of the aerodynamic bearing andbetween the lower inner circumferential surface of the hub and the outercircumferential surface of the main bearing body of the aerodynamicbearing.
 8. An aerodynamic bearing assembly as claimed in claim 1,wherein the air groove is formed both on the upper horizontal surface ofthe main bearing body of the aerodynamic bearing and on the lower innercircumferential surface of the hub to generate aerodynamic pressurebetween the lower horizontal surface of the hub and the upper horizontalsurface of the main bearing body of the aerodynamic bearing and betweenthe lower inner circumferential surface of the hub and between the outercircumferential surface of the main bearing body of the aerodynamicbearing.
 9. An aerodynamic bearing assembly as claimed in claim 1,wherein the air groove is formed both on the outer circumferentialsurface of the main bearing body of the aerodynamic bearing and on thelower horizontal surface of the hub to generate aerodynamic pressurebetween the lower inner circumferential surface of the hub and betweenthe outer circumferential surface of the main bearing body of theaerodynamic bearing and between the lower horizontal surface of the huband the upper horizontal surface of the main bearing body of theaerodynamic bearing.
 10. An aerodynamic bearing assembly as claimed inclaim 1, further comprising at least one oilless bearing, formed on theupper horizontal surface of the main bearing body of the aerodynamicbearing in a ring shape.
 11. An aerodynamic bearing assembly as claimedin claim 10, wherein the oilless bearing is provided with an air grooveof a predetermined depth on an upper surface thereof.
 12. An aerodynamicbearing assembly as claimed in claim 1, further comprising at least oneoilless bearing, formed on the lower horizontal surface of the hub in aring shape.
 13. An aerodynamic bearing assembly as claimed in claim 12,wherein the oilless bearing is provided with an air groove of apredetermined depth on a lower surface thereof.
 14. An aerodynamicbearing assembly as claimed in claim 1, further comprising at least onepair of oilless bearings opposite to each other, formed on the upperhorizontal surface of the main bearing body of the aerodynamic bearingand on the lower horizontal surface of the hub in a ring shape.
 15. Anaerodynamic bearing assembly as claimed in claim 14, wherein of theopposite oilless bearings, one, which is mounted on the upper horizontalsurface of the main bearing body of the aerodynamic bearing, is providedwith an air groove on an upper surface thereof.
 16. An aerodynamicbearing assembly as claimed in claim 14, wherein of the opposite oillessbearings, one, which is mounted on the lower horizontal surface of thehub, is provided with an air groove on a lower surface thereof.
 17. Anaerodynamic bearing assembly as claimed in claim 1, wherein the ballbearing for rotatably supporting the hub is arranged at a rotationalcenter of the aerodynamic bearing to be at a lower position than anupper horizontal plane of the main bearing body of the aerodynamicbearing, so that the ball bearing has a rotatable supporting point at alower position than the upper horizontal plane of the main bearing bodyof the aerodynamic bearing.
 18. An aerodynamic bearing assembly asclaimed in claim 1, wherein the ball bearing for rotatably supportingthe hub is arranged at a rotational center of the aerodynamic bearing tobe flush with an upper horizontal plane of the main bearing body of theaerodynamic bearing, so that the ball bearing has a rotatable supportingpoint flush with the upper horizontal plane of the main bearing body ofthe aerodynamic bearing.
 19. An aerodynamic bearing assembly as claimedin claim 1, wherein the ball bearing for rotatably supporting the hub isarranged at a rotational center of the aerodynamic bearing to be at ahigher position than an upper horizontal plane of the main bearing bodyof the aerodynamic bearing, so that the ball bearing has a rotatablesupporting point at a higher position than the upper horizontal plane ofthe main bearing body of the aerodynamic bearing.